Famous Schrodinger's cat hypothetical experiment says that cat is dead or alive until we open box and see condition of poor animal, which deserved better logic. Cat is always in some certain state - regardless from is observer able or not to see what the state is.

I had a similar issue and it turned out that the hub had come unstuck from the magnetic media and so the disk was not actually spinning. Just the hub. I ended up with a blank disk image as well. AtariZoll advice is good. Download a disk image from Atarimania and convert it to .ST format as the disk has no copy protection on it.